The deacon's ministry of the Word includes proclaiming the Gospel at the Eucharist, preaching and teaching.

His ministry of liturgy is at the altar, and includes various parts of the Mass proper to the deacon. At Mass, the deacon is the ordinary minister of the proclamation of the Gospel (in fact, a priest, bishop, or even the Pope should not proclaim the Gospel if a deacon is present) and of Holy Communion (primarily, of the Precious Blood). Deacons typically have the faculty to preach the homily at Mass, at a frequency determined by the pastor.

The ministry of charity involves service to the poor and marginalized and working with parishioners to help them become more involved in such ministry.

Deacons are clerics, they can administer the sacrament of Baptism and serve as the church's witness at the sacrament of Holy Matrimony, which the bride and groom administer to each other. Deacons may preside at various services such as a wake service, and Benediction of the Blessed Sacrament, and they may give blessings. They cannot hear confession and give absolution, anoint the sick, or celebrate Mass.

The vestments most particularly associated with the Roman Catholic deacon are the alb, stole and dalmatic. Deacons, like priests and bishops, must wear their albs and stoles; deacons place the stole over their left shoulder and it hangs across to their right side, while priests and bishops wear it around their necks.

Permanent deacons often serve in parish or other ministry as their time permits, since they typically have other full time employment. They may also act, with permission of the Bishop, as parish administrators. With the passage of time, more and more deacons are serving in full-time ministries in parishes, hospitals, prisons, and in diocesan positions. Deacons often work directly in ministry to the marginalized inside and outside the church: the poor, the sick, the hungry, and the imprisoned.